Composting device

ABSTRACT

A composting device including a drum rotatably arranged about an axis slightly inclined to the horizontal, and having a feeding opening for composting material at the higher situated side of the drum and a discharge opening for finish composted material at the lower side of the drum, the interior of the drum being subdivided into a number of consecutive chambers arranged in the longitudinal direction of the drum, with intermediate sieve screens, whereby the adjacent chambers of the drum are entirely separated from each other by the sieve screens, whereby each sieve screen has the same size of meshes over its entire surface, and where each sieve screen has smaller mesh size in relation to the nearest preceding sieve screen.

BACKGROUND OF THE INVENTION

Composting is an excellent method of letting the nature take care of thedegradation of organic waste, such as parts of plants, domestic wasteand the like. Under different climatic conditions there are putdifferent demands onto the structural design and shape of the compostingplants, but it is a common positive thing for different plants,different temperatures and moisture contents, and for different materialthat is to be decomposed, if the material continuously is supplied withoxygen necessary for the degradation.

For this purpose it earlier has been suggested to design the compostingdevice, as a drum rotatably arranged about a horizontal or slightlyinclined axis and having a net covered outer side, which at the slowrotation (if the drum on one hand turns the material in the drummechanically and on the other hand allows the oxygen of the air to reachthe material to a big extent. Such a device is known e.g. from U.S. Pat.No. 3,966,415, but the disadvantage with this device is that the outsidewall of the drum, which is provided with net meshes of uniform size,will spread the degraded material over a distance equal to the drumlength, at the same time as different fractions of the degraded materialwill be mixed with each other. Furthermore with this device there is therisk that more coarse material, that lies closer to the drum wall, mayprevent discharge of more degraded material situated closer to thecentre of the drum.

From U.S. Pat. No. 3,245,759 is known a plant for fermentation oforganic material, which works with forced air through-flow, and whichconsists of an elongated cylindric drum, rotatable about an axis beingslightly inclined to the horizontal. At the infeed end of the drum isprovided a sieve, against which material to be treated is advanced by ascrew. After the sieve the interior of the drum is divided by a numberof partition walls into a number of closed fermentation chambers,situated one after the other, and which partition walls each having oneopening, which during a short part of a revolution of the drum transfersmaterial from one chamber to the chamber situated nearest thereafter.

CA-B-613,004 describes a composting plant with a horizontally arrangedrotatable drum, the interior of which is divided by sieve walls, each ofwhich has a large central opening and a number of smaller meshes. Allsieve walls are identical, i.e. they have the same mesh size, and thisimplies that no uniform size of particles is obtained at the dischargeside of the plant, which is also further accentuated by the fact thatlarger non-mouldered pieces can pass to the next section through thelarge central openings of the sieve walls.

The purpose and most important features of the invention

The purpose of the invention is to provide a composting device, by meansof which the entire compost mass is supplied with oxygen in a simple andefficient way without forced air supply, at the same time as alldegradable material will be disintegrated into an essentially uniformfraction, which can be collected in a simple way, and which devicefurthermore must be reliable and comparatively cheap to obtain and tooperate, and this has been achieved by means of the characteristicsdefined in the accompanying claims.

DESCRIPTION OF THE DRAWINGS

The invention will be further described herebelow with reference to anembodiment shown in the enclosed drawing,

FIG. 1 shows in perspective a composting device according to theinvention, whereby the outer wall of the drum is merely indicated incontours, and

FIG. 2 is a detailed view in bigger scale of a solution for rotation ofthe drum.

DESCRIPTION OF PREFERRED EMBODIMENT

In FIG. 1 is shown, in perspective, a composting device according to theinvention, which includes a cylindric drum 1, which is rotatablysupported in a frame 2 about an axis slightly inclined against thehorizontal. For the sake of clarity the envelope surface of the drum isshown transparent in the drawing figure, but it is preferably designedas a closed, untransparent cylindric wall, with or without insulatinglayer. In the upper gable of the drum is provided a centrally locatedfeeding opening 3 to the outside of which is connected a feeding hopper4 for material that shall be composted. In the lower gable of the drumis arranged, in a similar way, a centrally located discharge opening 5,to which is connected a discharge funnel 6, a sack 7 for collectingfinish composted material being connected thereto in the embodimentshown. In connection to the discharge opening 5, the interior of thedrum is provided with inclined fixed guiding walls 8, arranged to guidethe compost material towards the central discharge opening 5 at rotationof, the drum.

In the embodiment shown the drum 1 has three circumferential, externalgear rings 9, via which the drum is rotated by means of transmissionfrom a driving motor 10 are by means of a gear drive 12 arranged on theaxis 11 parallel with the drum.

The interior of the drum 1 is divided into a number of spaced apartcheers 13, 14, 15, whereby the dividing means consist of sieve screens16, 17, of which the one 16, nearest to the feeding opening 3 has bigmeshes, whereas the mesh size in the following sieve screen 17 issmaller. In the embodiment shown there are only two sieve screens, whichconsequently subdivide the drum into three chambers, but it isunderstood that the device can be provided with further sieve screens,which subdivide the drum into further chambers, with gradually reducedmesh size in the sieve screens.

The envelope surface of the drum is preferably equipped with sectionsthat could be open, represented in the figure by locking hooks 18.

When the material to be composted is introduced in the feeding hopper 4it will reach the first chamber 13 through the feeding opening 3. Thelongitudinally slightly inclined drum is put in temporary rotation, e.g.5-6 revolutions during a period of approximately 60 seconds once or sometimes in twentyfour hours. As the material in the first chamber 13 isdegraded, it will, due to the inclination and temporary rotation of thedrum, tend to travel through the first sieve screen 16, whereby howeverparticles which are to big are retained in the first chamber 13 forfurther decomposition. Material, which in this manner is fed into thesecond chamber 14 via the first sieve screen 16, thereby has a certainmaximum size. Smaller particles can travel directly through the secondsieve screen, and after further decomposition in the second chamber theremaining material therein will be able to pass through the second,fine-meshed sieve screen 17, so that a rather uniform fraction willreach the third and last chamber 15 in the embodiment shown, from wherethe uniform finish composted material is discharged through thedischarge opening 5 by means of the guiding walls 8, for thereafterbeing collected in an appropriate way, e.g. in sacks, in a wheelbarrowor the like.

In FIG. 2 is shown, in bigger scale, a section of a composting deviceaccording to the invention with a somewhat modified design of thedriving means for the drum, whereby a driving motor 19 is provided witha timer 20 for turning on the motor at desired occasions. Here the motoris located at one of the drum gables but it is otherwise, in conformitywith the embodiment according to FIG. 1, arranged to transfer itsrotation via a common axis 21 to a number off gearwheels, in this casesituated behind the housing 22, and cooperating with gear rings 23 alongthe circumference of the drum.

With a comparatively simple and inexpensive device in this manner isobtained very good oxygenization of the composting material, at the sametime as there is a continuous advance of increasingly degraded materialto the discharge side where the discharged material has e uniform size.

The invention is not limited to the embodiment shown in the drawing anddescribed in connection thereto, but modifications and variants mayoccur within the scoop of the following claims. Even if the drum hasbeen illustrated and described without any fixed inner shaft, it mayalso be proper to use an embodiment having a fixed centre shaft, aboutwhich the drum is brought to rotate, and which shaft supports firmlymounted brushes, arranged during rotation of the drum to brush againstthe sieve screens and to guide material through the sieve screens and toremove bigger particles that have been caught thereon.

We claim:
 1. A composting device comprising a drum rotatably arrangedabout an axis lightly inclined to the horizontal, and having a feedingopening for composting material at the higher situated side of the drumand a discharge opening for the finished composted material at the lowerside of the drum, the interior of the drum being subdivided into anumber of consecutive chambers arranged in the longitudinal direction ofthe drum, with intermediate sieve screens wherein said adjacent chambersof the drum are entirely separated from each other by said sieve screenseach sieve screen having the same size of mesh over its entire surfaceand a smaller mesh size in relation to the nearest preceding sievescreen.
 2. A composting device according to claim 1, wherein said drumis equipped with rotatable means arranged to temporarily rotate the drumabout its longitudinal axis.
 3. A composting device according to claim2, wherein said rotatable means include a motor controlled by a timer.